What is caffeine?

Caffeine is known as a ‘central nervous system stimulant,’ and is a natural chemical found in various parts of plants; including coffee and cocoa beans, and tea leaves.

That buzz we get from caffeine is a result of the way that it blocks chemicals in our body that cause fatigue, and stimulates our nervous system, prompting the ‘fight or flight’ responses that make us run faster or push harder.

The performance advantage

The buzz we get off our morning cup of coffee doesn’t only improve our concentration and performance during mental activities, but also during a workout, whether that’s a set of intervals on the bike, a crushing cross-fit session, or brutal boxing class.

Here are the key ways that caffeine improves our performance:

Improved alertness:

Improved alertness and concentration gives us a massive advantage in skill-based activities such as racket or ball sports – our perception and co-ordination improves and refines our technique and judgement.

Mental alertness also gives a great boost to endurance activities too, such as running, cycling and swimming. The more awake we feel, the more determined and focused on achieving something we are. When we’re tired, we’re more likely to fail a set of intervals or miss our pace targets as the willpower required to achieve it flounders. As such, blocking this sense of fatigue puts us on the front foot.

Improved fuelling:

We have two major sources of energy in our body – carbohydrate and fat. Even the skinniest of us have huge fat reserves that could fuel us for days, but only limited carbohydrate stores.

Caffeine makes us prioritise fat over than glycogen (carbohydrate) as our primary source of energy, and so boosts our endurance and improves our body composition as we burn the blubber.

By predominantly burning fat before carbohydrate as you train, you save your carbohydrate stores - which typically fuel the most intense efforts – for when you need it most, such as the crucial last minutes of a race or final reps of a workout.

Improved blood flow:

Caffeine helps oxygen flow through our body and so improves the delivery of fuel to our muscles. Caffeine in the bloodstream causes our blood vessels to expand (vasodilate), giving our body a richer source of oxygen.

Dosage

Lab testing has proven that both strength and endurance athletes require somewhere between 3 – 6mg of caffeine/kg body mass to see a performance boost.

That doesn’t mean you should just shoot for the high end and try to get 6mg/kg straight away. As you’ll know from that day when you had one too many coffees at work, too much caffeine in your system has some serious side effects, including anxiety and dizziness - and, of course, sleeplessness.

Everyone has a different tolerance of caffeine depending on their build, genetics and extent of habitual use, so you need to experiment to find where your threshold lies. If you’re looking to boost a workout, start off at 3mg/kg before a session and see how you feel.

Whatever you do though, don’t exceed 400mg caffeine in total in a day (the medically prescribed maximum recommendation), and don’t make heavy doses of caffeine commonplace, or it will place your heart under stress.

Caffeine content of one coffee or one tea can vary significantly from the next, but as a ballpark, expect a cup of filter coffee to contain c.150mg caffeine, a single espresso to contain 100mg, or a cup of black tea to contain c.30mg.

Timing

The speed at which caffeine has a noticeable impact on our system differs from individual to individual, just as required dosages alter between us all. What’s more, caffeine absorption and impact differs according to our blood sugar level – the more rich with glycogen our blood is, the better the metabolism of the chemicals within it. The way in which sugar and caffeine makes such a powerful combination is why it can feel like a sugary coffee gives more of a kick than one without, or why we get such a boost from a packaged carb-caffeine gel.

As a rule of thumb, caffeine starts having a noticeable impact on our system 20-30 minutes after ingestion, and peaks after around 1-2 hours. So, if you want to use caffeine as a performance boost, try getting some on board around 30-60 minutes before a session – depending on the length of your workout and when you want to feel at your best (for example, at the very start or end of a running or cycling race, or as you hit a key moment of your weights session).

For long workouts such as a marathon or triathlon, you may want to ‘top up’ with caffeine drinks or gels. When you do this, remember the half-life of caffeine is around 5 hours, means that if you took 200mg caffeine at 8am, you will still have around 100mg in your bloodstream at 1pm. Knowing this should give you a feel for how much you need to top up.